This invention relates to a device for connecting a heat exchange pipe, which is most often a radiant pipe that is intended for heating a pressurized reactor, and said reactor. The reactor that is described, for example, in U.S. Pat. No. 5,554,347 of the applicant usually comprises, in the case where chemical reactions are carried out that require at least at start-up an input of calories, a series of elements that make possible at least in a first zone a supply of heat that is necessary to the start-up of the reaction. The teaching of this patent is to be considered as an integrating part of this description solely from the fact of its citation. This reactor can be used for reactions that are exothermic overall but that require the input of calories at the start-up, such as, for example, the catalytic hydrogenation reactions. This reactor is more particularly applicable to the implementation of any endothermic reaction but more particularly for the implementation of reactions of steam-cracking, pyrolysis, catalytic dehydrogenation and catalytic vaporeforming of hydrocarbons or hydrocarbon fractions in which the reaction temperature is most often higher than about 350xc2x0 C. and where one of the problems to be solved is to limit the secondary reactions that lead to the formation of tar and/or coke.
The walls play an important role in heat exchange, since they can absorb the radiation that is emitted by the jackets of the heat exchange means, and consequently the temperatures of these jackets and walls have a tendency to attain equilibrium. It is then possible to increase in particular the exchange surface and virtually to double it by designing the device in a special way. Actually, although the heat exchange means can be placed at random, it is preferable, for the purpose of increasing the exchange surface, to place these heat exchange means so that they are aligned, which makes it possible to produce n rows of m heat exchange means in terms of the length (for a total number of heat exchange means equal to (nxc3x97m), thus at least one longitudinal zone and most often at least two longitudinal zones that each comprise at least one and often several layers of heat exchange means will be formed, whereby each longitudinal zone is separated from the next by a wall that is made of a refractory material. It thus is possible to increase the heat exchange surface by an optimized surface such as, for example, by the addition of flanges on the outside jackets of the heat exchange means that take part in the heat transfer.
By radiation, the temperature of these walls increases and has the tendency to reach a value that is very close to that of the outside jackets of the heat exchange means. These walls therefore will also play a role in the heating of the process gas by convection. Thus, in this embodiment, whereby the exchange surface is significantly increased, it will be possible to obtain the same process gas temperature with a temperature of the outside jackets of the heat exchange means and walls of a relatively smaller thickness, which consequently makes possible a reduction of the coke formation. In a particular embodiment that is described in, for example, U.S. Pat. No. 5,554,347, each longitudinal zone will comprise a single row of heat exchange means.